Radiology Imaging Role for Interstitial Lung Disease (ILD)
Idiopathic Pulmonary Fibrosis (IPF) is the most common ILD and carries a high mortality rate, so it is important to differentiate IPF from the remainder of the ILDs. It usually occurs in patients over the age of 50 years and is more common in men.
The treatment of IPF is different than the other ILDs and includes new antifibrotic medications and lung transplant, in addition to the traditional treatment of corticosteroids and immunosuppressive drugs.
The key role of radiologists is to identify patients with Usual Interstitial Pneumonitis (UIP), which is the radiographic equivalent of IPF because of the substantially poorer prognosis than the other ILDs.
The textbook UIP pattern on High Resolution Chest CT is lower lung predominant honeycombing, subpleural reticulation and groundglass opacity, as well as associated traction bronchiectasis.
The Diagnosis of IPF requires the exclusion of other known causes of ILD which are called Nonspecific Interstitial Pneumonitis (NSIP). Mimickers of IPF which could have different prognosis and treatment include: Collagen Vascular Disease, Hypersensitivity Pneumonitis, Desquamative Interstitial Pneumonitis which is smoking related, Occupational Exposure, and Drug reaction.
In all patients suspected to have ILD who do not show typical clinical and radiologic features of UIP, lung biopsy should be considered. These are the patients without honeycombing on their High Resolution Chest CT.
Nonspecific Interstitial Pneumonitis (NSIP) is an area of diagnostic uncertainty, and its diagnosis should be provisional until further workup and characterization are completed. This could include bronchoalveolar lavage, serologic workup for autoimmune Collagen Vascular Diseases (Rheumatoid Arthritis, Lupus, Scleroderma, etc), standardized questionnaire regarding occupational, precipitant, and drug exposure.
Close interaction between clinicians, radiologists, and pathologist is crucial in establishing the final diagnosis in ILD patients.